1. Field of the Invention
The present invention relates to an image processing apparatus such as a scanner.
2. Description of the Related Art
Typically, an image processing apparatus incorporating a contact image sensor (hereinafter referred to as “CIS”) has a pixel arrangement in sensor chips of the CIS in which pixels are aligned in a line along the main scanning direction. In such an image processing apparatus, signals from the pixels are output from the sensor chips through a single output unit, where image processing operations such as analog-to-digital (A/D) conversion and shading compensation are performed.
There has been an increasing demand for a high resolution image processing apparatus incorporating a CCD (charge coupled device) with a reduction optical system, as well as a high resolution image processing apparatus incorporating a CIS. Since the CIS is a non-magnifying optical system, it essentially requires pixels with small light receiving units in order to provide high resolution; however, in this case, it is difficult to maintain the sensitivity of the CIS at the desired level.